https://ieeexplore.ieee.org/document/7241769^^^
All tracks are companded. Tracks No. 1 and No. 3 are matrixed to form the left and right front and back channels. Track No. 2 forms the center front channel. Track No. 4 was not used initially...
Edit (some Quintaphonic specs):
https://groups.google.com/g/rec.arts.movies.tech/c/Gn3fkSr96_4
Anyone with a subscription to the SMPTE Journal (maybe some specifics of Quintaphonic sound could be posted in QQ)?
IIRC, Audio mag had a writeup about the Tommy movie (the showing took place at a high class movie theater, there was a mixing board + audio engineer in the theater fine tuning the mix as the movie played), I'm still looking in worldradiohistory.com for the writeup.
Due to the Audio article, I saw Tommy in 1975-09 (in glorious mono), I was mesmerized by the movie, I stayed to the very end of the credits just to see if there was any Quintaphonic credit.
I bought the soundtrack LP asap, it never occurred to me that the LP might be QS encoded.
Kirk Bayne